To solve the given problem, we need to address two parts: finding a point estimate for the proportion and computing a 95% confidence interval for the population proportion.
(a) Point Estimate for the Proportion:
The point estimate for the proportion of potsherds with the three-circle, red-on-white pattern is calculated using the formula for the sample proportion:
\[ \hat{p} = \frac{x}{n} \]
where \( x \) is the number of potsherds with the pattern, and \( n \) is the total number of potsherds in the sample.
Given:
- \( x = 70 \)
- \( n = 161 \)
\[ \hat{p} = \frac{70}{161} \approx 0.4348 \]
So, the point estimate \( \hat{p} \) is 0.4348.
(b) 95% Confidence Interval for the Population Proportion:
To compute the 95% confidence interval for the population proportion, we use the formula:
\[ \hat{p} \pm Z \times \sqrt{\frac{\hat{p}(1-\hat{p})}{n}} \]
where \( Z \) is the Z-score corresponding to the desired confidence level. For a 95% confidence interval, \( Z \approx 1.96 \).
First, calculate the standard error (SE):
\[ SE = \sqrt{\frac{0.4348 \times (1 - 0.4348)}{161}} \approx \sqrt{\frac{0.4348 \times 0.5652}{161}} \approx \sqrt{\frac{0.2458}{161}} \approx 0.0388 \]
Now, calculate the margin of error (ME):
\[ ME = 1.96 \times 0.0388 \approx 0.0760 \]
Finally, compute the confidence interval:
\[ \text{Lower limit} = 0.4348 - 0.0760 = 0.3588 \]
\[ \text{Upper limit} = 0.4348 + 0.0760 = 0.5108 \]
Thus, the 95% confidence interval for the population proportion is:
0.359 to 0.511 (rounded to three decimal places).